docs(readme): syntax-highlight the darkmode snippet as html

README.md

@@ -51,7 +51,7 @@ If you are only interested in generating a svg, consider using this faster actio
 
 For **dark mode** support on github, use this [special syntax](https://docs.github.com/en/get-started/writing-on-github/getting-started-with-writing-and-formatting-on-github/basic-writing-and-formatting-syntax#specifying-the-theme-an-image-is-shown-to) in your readme.
 
-```md
+```html
 <picture>
   <source media="(prefers-color-scheme: dark)" srcset="github-snake-dark.svg">
   <source media="(prefers-color-scheme: light)" srcset="github-snake.svg">